Jun 6th 2015 |

Finding Objects

The Best Way to Begin

There is no better way to start learning the stars than with a planisphere. A planisphere is a flat, circular chart that can be set to any date and time. Once set, the charts shows the entire sky laid out exactly as it appears for that particular date and time. Planispheres are basic charts, usually showing only the brightest constellations and sometimes a few brighter deep sky objects. This is great for a beginner as it does not overwhelm you with too much detail. When starting out, you need to learn the biggest, brightest patterns in the sky, like the Big Dipper and Orion. Later you can use these guideposts to navigate to obscure constellations like Vulpecula or Lynx, but there is no need to concern yourself with these when just starting out.

Of course, finding an observing companion who already knows the sky is very helpful. Most amateur astronomers are thrilled to share the sky with others. One of the great things about astronomy is that it seems to engender a culture of teaching and enthusiasm. Joining a local astronomy club is recommended as a great way to learn all about the hobby.

Finding the Constellations

Most new astronomers look up at the sky and wonder what sort of mind-altering substances the ancients were ingesting when they came up with the constellation patterns. The thing to remember is this: the constellations do not necessary form specific shapes in the sky; rather, they group stars together in a way that is easier to remember. Some constellations certainly have the appearance one would expect from their names. Scorpius looks like a scorpion, Leo is shaped like a lion, and Orion has a vaguely human figure. But Ophiuchus looks like a barn rather than a serpent bearer, Pegasus appears to be a baseball diamond instead of a flying horse, and Perseus looks more like a vacuum cleaner than a Greek hero. The key is to find a pattern that you can remember, no matter what it is. Sagittarius looks like a teapot. Pisces looks like a big V. Ursa Major looks more like a cosmic anteater than a bear. Imagine the star patterns however you want, as long as you can remember them. A couple great books for picking out easy-to-remember star patterns are the classics The Stars and Find the Constellations by H. A. Rey (of Curious George fame).

Also, don’t worry about learning all 88 constellations. You don’t memorize every street in your home town, right? Just like a knowledge of the major intersections in a city will get you around, you only need to know the biggest and brightest star patterns. From there a star chart can get you the rest of the way to obscure parts of the sky. Even just knowing a few bright stars like Arcturus, Sirius, and Capella can get you around the sky to begin with. You can find a lot of stars and constellations just from one jumping off point. The Big Dipper points to the stars Polaris and Arcturus, and finding fainter constellations like Canes Venatici from the Dipper is easy. Knowing how to identify just the Big Dipper, Orion, and Cassiopeia can be enough to start navigating the heavens. Start simple and work up from there. You’ll be surprised how quickly you can learn the sky.

Starhopping

The basic method for finding an object is to locate the constellation it is in, then use the pattern of nearby stars to zero in on the target. An easy example is finding the Orion Nebula. Orion is a distinct constellation of bright stars in the winter sky. The most prominent star pattern is Orion’s belt of three stars. Dropping down from this leads to three faint stars that make Orion’s sword. The middle “star” is actually the Nebula itself. This is an easy starhopping task since the object itself is visible.

But finding objects too faint to see with the unaided eye is not hard either. A good example is M13, the Hercules Cluster. Finding Hercules is a bit more difficult than Orion, since it is a much fainter constellation. But it is located near Arcturus, one of the brightest stars in the sky and easily located from the Big Dipper. A quick look at a planisphere will show that Hercules appears below Arcturus when rising in the east, and above it when setting in the west. Hercules looks a bit like a bowtie, and M13 is located along one edge of the bowtie, about a third of the way between two stars. A look at a moderately detailed star chart will show this. The trick then is just pointing the telescope to that place in the sky. This is where a reflex finder like a Telrad is immensely helpful. Instead of showing a magnified view of the sky, upside-down and backwards like afinderscope, a reflex finder just shows the spot in the sky where the telescope is aimed. Finding a spot between two stars is very simple.

Cheating

Of course, when all else fails you can turn to a computerized telescope to find objects for you. But this only helps so much. It does no good to randomly punch in some number like NGC2915 because it might be a 13th magnitude galaxy only visible from the southern hemisphere (which it is, by the way). You’ll still need to know what constellations are out when in order to pick out some good objects to view. If you know from looking in a guide that you want to see the Lagoon Nebula, it is helpful to know whether Sagittarius is out or not. In December it’s not and in July it is. But can you see it from where you are or are there trees in the way?

One nice thing about learning the sky with a computerized scope is that as long as you know roughly where an object is located–what constellation and whether it is up–the telescope can do the last step of actually finding the object. This saves you the trouble of starhopping but still requires that you have a basic knowledge of the sky. If you use a reflex finder such as a Telrad, you can easily see exactly where an object is after the telescope locates it. In this way, a computerized telescope actually helps, rather than hinders, learning the sky.